This invention relates to an electro-chemical apparatus for monitoring and/or measuring a component of a gas, either in ambient atmosphere or a gas stream.
An electrochemical device for detecting and/or monitoring a component of a fluid is known from United Kingdom Patent Specification No. 1,552,620 in which a reagent which is static relative to the electrodes of the device comprises an aqueous solution of a deliquescent substance. One example of a suitable reagent is calcium bromide where the gas to be detected is a halogen such as chlorine. The effect of the deliquescent substance is to discourage drying out of the device by loss of water from the reagent by countering this loss by adsorption of water from the fluid, for example a gas such as atmospheric air, being monitored. Using the above reagent, chlorine can be detected because it liberates bromine from a solution of calcium bromide according to the following reaction. EQU Cl.sub.2 +2Br.sup.- .fwdarw.Br.sub.2 +2Cl
However hydrogen halides, for example hydrogen fluoride (HF) have no effect on this reagent. It was suggested in "Electrometric Detection of Corrosive Gases" J Morrow, ISA AID 72408 (31-36) USA, 1972 that a bromide/bromate electrolyte could be used for detecting hazardous levels of acidic gases including HF, but no teaching more precise than this was offered.